It is known that in the operation of some machines, ozone and other noxious gases are generated. For example, noxious gases, including ozone, are generated in electrostatographic copying machines as a result of corona discharge. Corona discharge devices are employed in electrostatographic copying machines for the charging or sensitization of the photosensitive member as well as at certain other stations within the copying machines. It is also known that the problem of the formation of ozone and other noxious gases during the operation of corona discharge devices is more acute at higher levels of output of corona charging. As indicated in U.S. Pat. No. 3,983,393, increased copy speeds, as well as other requirements placed on modern copying and duplicating machines, have resulted in needs for higher outputs from the corona devices.
The detrimental effects of such noxious gases on machine components and people are well known. Relatively low concentrations of ozone in the atmosphere, for example, from 1 part per 1,000,000 to 10 part per 1,000,000, can cause headaches and nausea and irritation of mucous membranes. Ozone and other noxious gases generated in the operation of corona charging devices may also detrimentally affect the performance of the photosensitive member in copying machines. Thus, there is a need for an economical and high efficiency method and apparatus for the removal of ozone and other noxious gases.
In IBM Technical Disclosure Bulletin, Vol. 11, No. 8, January 1969, page 944, there is disclosed an ozone filter for electrophotographic copying apparatus which consists of a rectangular and generally plate-like filter whose active ingredient is charcoal impregnated with sodium iodide. Only air from a brush cleaner is collected for filtration and the air near the corona charging units are not collected and filtered. Thus, the IBM device is not particularly directed to those parts of the copying machine which are the points of generation of the ozone.
In U.S. Pat. No. 3,675,096, there is disclosed a corona discharge device in which an elongated knife-edged electrode is enclosed in a housing. The corona generated at the electrode passes out of the housing and onto the surface of a photoconductive layer through a foraminous screen. The interior walls of the housing as well as the screen are coated with a catalytic material, such as silver, to convert ozone formed by the corona discharge to oxygen.
In U.S. Pat. No. 3,862,420, there is disclosed an apparatus for supplying filtered air to a corona discharge device, used to charge a photoconductor in an electrophotographic apparatus, to eliminate contamination within the corona unit. This is done by filtering the air supplied to the corona discharge device first through a particle filter and then through an ammonia filter. The outlet air from the corona discharge device is then passed through an ozone filter. No specific information is provided on the ozone filter, and no filtering system is provided for the transfer and preclean corona devices.
In U.S. Pat. No. 4,040,731, there is disclosed an electrophotographic apparatus having a screen-type photoconductive drum. Since the photoconductive element in such an apparatus is degraded by contact with ozone, this patent proposes to supply air to the screened drum to remove detrimental gases such as ozone and dust produced in a corona charge device. However, there is no provision in this patent for collecting and filtering the air from the corona charge devices.
Finally, in U.S. Pat. No. 4,143,118, there is disclosed an apparatus and method for ozone reduction in electrostatographic reproduction equipment. In the apparatus and method of that patent, ozone rich gases are directed through a fluidized bed reactor in which a bed of catalytically active granular material is fluidized by the ozone laden vapors. The reactor is provided with means for purging fine particles from the perforated wall of the catalyst-containing chamber proximate to the exhaust end of the reactor to prevent such fine particles from becoming permanently entrained. This patent, then, demonstrates one method and apparatus for the removal of ozone rich gases from the area of the corona discharge electrodes, which another prior art patent has termed "not always easy to construct and arrange". See U.S. Pat. No. 4,040,731 at column 2, lines 23-28.
While several devices and approaches have been shown in the prior art for the collection and/or removal of ozone generated at corona discharge devices, there is a continuing need for improved method and apparatus for the collection and removal of ozone and other noxious gases. This is particularly true for new high volume and high speed copying and duplicating machines.
Accordingly, it is an object of the invention to provide an improved method and apparatus for the collection and removal of ozone and other noxious gases generated in machines.
It is another object of the present invention to provide an improved method and apparatus for the removal of ozone and other noxious gases generated by corona discharge devices in electrostatographic copying machines.
It is a further object of the invention to provide an improved method and apparatus which will efficiently and economically collect and remove ozone and other noxious gases generated by corona discharge devices, so that OSHA and other government regulations can be met for the life of the copying machine.